34 DISINFECTANT 



tills. It is a silicate of protoxide of copper, and is found in veins in limostono in 

 the Kirghis Steppes. See COITKK. 



DIOPTRIC LIGHTHOUSES. See LIGHTHOUSES. 



DIORITE. An igneous rock composed of a crystalline-granular mixture of a 

 triclinic felspar and hornblende. It is often so fine-grained in texture that it is diffi- 

 cult to determine the component minerals. Diorite generally presents a dark green 

 colour, and is one of the rocks commonly included under the general name of ' green- 

 stone.' 



DIP. When any stratum, mineral vein, or dyke, does not lie horizontally it is said 

 to dip E. W. N. or S., as the case may be. The angle which it makes with the 

 horizon is called the angle of the dip. 



DIPPEIi S ANIMAIi OZZi. A fetid volatile oil obtained when animal sub- 

 stances, such as bone, are subjected to distillation. That which is found in commerce 

 is obtained in the manufacture of bone-black. 



DIPPING. Ornamental works in brass are usually brightened by a process called 

 dipping. After the work has been properly fitted together and the grease removed, 

 either by the action of heat, or by boiling in a pearlash-lyo, it is pickled in a bath of 

 dilute aqua fortis. It is then scoured bright with sand and water, and being well 

 washed is plunged into the dipping bath, which consists of pure nitric acid, commonly 

 known as dipping aqua fortis, for an instant only, and is then well washed with cold 

 and hot water to remove every trace of acid from the surface, after which the work is 

 put into dry beech or box wood sawdust, &c., well rubbed until it is quite dry, and 

 then burnished and lacquered. See DEAD-DIPPING. 



DISCRASXZ or I>ISCRASITE. An antimonial silver ore. of rare occurrence. 



DISINFECTANT. A substance which removes the putrid or infected condition 

 of bodies. It is well not to confound it with antiseptic, which applies to those bodies 

 which prevent putrefaction. The word ' disinfectant ' has lately become somewhat 

 uncertain in its meaning, on account of a word being used as its equivalent, viz. deodo- 

 riser. This latter means a substance which removes odours. In reality, however, 

 there are no such substances known to us as a class. There are, of course, some 

 substances which destroy certain others having an odour, but in all cases the removal 

 of the smell and the destruction or neutralisation of the vapour or gas causing the 

 smell must be simultaneous. There is, however, a large class of substances that destroy 

 putrefaction, and the name ' disinfectant ' is therefore distinctly needed. The gases 

 which rise from putrefying bodies are not all capable of being perceived by the senses in 

 their ordinary condition, but sometimes they are perceived. A disinfectant puts a 

 stop to them and deodorises simultaneously. If any substance were to remove the 

 smell of these gases, it would remove the gases too, as they are inseparable from their 

 property of affecting the nose. A deodoriser would therefore be, and is, a disinfectant 

 of that gas the smell of which it removes. But it has been suggested that it may 

 remove those gases which smell, and allow the most deleterious to pass, they having 

 no smell. Whenever wo find such a class of substances, it will be well to give them 

 the name of ' deodorisers.' There may be some truth in the hypothesis that metallic 

 salts remove the sulphur, and by preventing the escape of sulphuretted hydrogen causo 

 less odour, without complete disinfection. So far as wo know, however, there is a 

 disinfecting action along with the deodorising. Any solution having the effect hero 

 supposed would at the least be a partial disinfectant, inasmuch as the decomposition 

 would be so far put a stop to, as to prevent at least one obnoxious gas. To prevent 

 the formation of one gas is to arrest decomposition or to alter the whole character of 

 the change which is producing the gases. The most deleterious of emanations have 

 no smell at all to the ordinary senses, and we can only judge of the evil by its ulterior 

 effects, or the fact that the substances capable of producing it are near, or by tho 

 analysis of the air. The cases where sulphuretted hydrogen accompanies the often si vo 

 matter are chiefly connected with fecal decomposition. This gas is a useful indica- 

 tion of the presence of other substances. So far as is known, the destruction of the 

 one causes the destruction of the other. But the presence of sulphuretted hy 

 is no proof of the presence of infectious matter, nor is its absence a proof of the 

 absence of infectious matter, it being only an occasional accompaniment. When the 

 infectious matter and the odoriferous matter are one, then to deodorise is to di^ 

 We can find no line of duty to be performed by deodorisers, and no class of bodies 

 that can bear the name, although there may be a few cases where tho word may be 

 found convenient. If, for example, wo destroy one smell by superadding a greater, 

 that might in one sense bo deodorising. If wo added an noid mr-tallic salt, and 

 removed tho sulphuretted hydrogen, letting loose those organic vapours which for 

 awhile accompany this act, we might, to those who were not very near, completely 

 destroy smell, and still send a substance into tho air by no means wholesome; but in 

 such a case decomposition is stopped, at least for awhile. The word 'deodorisers' may 



